The world's urban population in 1950 of just 746 million has increased to 3.9 billion in the decades since.[1] In 2009, the number of people living in urban areas (3.42 billion) surpassed the number living in rural areas (3.41 billion) and since then the world has become more urban than rural.[2] This was the first time that the majority of the world's population lived in a city.[3] In 2014 there were 7.25 billion people living on the planet,[4] of which the global urban population comprised 3.9 billion. The Population Division of the United Nations Department of Economic and Social Affairs at that time predicted the urban population would grow to 6.4 billion by 2050, with 37% of that growth to come from three countries: China, India and Nigeria.[1]

Urban areas are created and further developed by the process of urbanization. Urban areas are measured for various purposes, including analyzing population density and urban sprawl.

Unlike an urban area, a metropolitan area includes not only the urban area, but also satellite cities plus intervening rural land that is socio-economically connected to the urban core city, typically by employment ties through commuting, with the urban core city being the primary labor market.

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European countries define urbanized areas on the basis of urban-type land use, not allowing any gaps of typically more than 200 metres (220 yd), and use satellite imagery instead of census blocks to determine the boundaries of the urban area. In less-developed countries, in addition to land use and density requirements, a requirement that a large majority of the population, typically 75%, is not engaged in agriculture and/or fishing is sometimes used.

Argentina is highly urbanized.[5] The ten largest metropolitan areas account for half of the population, and fewer than one in ten live in rural areas. About 3 million people live in Buenos Aires City and the Greater Buenos Aires metropolitan area totals around 13 million, making it one of the largest urban areas in the world.[6]

The population is unequally distributed amongst the provinces: about 60% live in the Pampa region (21% of the total area), including 15 million people in Buenos Aires Province; Córdoba ProvinceSanta Fe Province and the Autonomous City of Buenos Aires have 3 million each. Seven other provinces have over one million people each: Mendoza, Tucumán, Entre Ríos, Salta, Chaco, Corrientes and Misiones. Tucumán is the most densely populated with 60 per square kilometre (160/sq mi), the only Argentine province more densely populated than the world average, while the southern province of Santa Cruz has around 1 inhabitant per square kilometre (2.6/sq mi).

In Australia, urban areas are referred to as "urban centres" and are defined as population clusters of 1,000 or more people, with a density of at least 200/km2 (518/sq mi)[9] Australia is one of the most urbanised countries in the world, with more than 50% of the population residing in the 5 biggest cities.

According to IBGE (Brazilian Institute of Geography and Statistics) urban areas already concentrate 84.35% of the population, while the Southeast region remains the most populated one, with over 80 million inhabitants.[11] The largest metropolitan areas in Brazil are São Paulo, Rio de Janeiro, and Belo Horizonte — all in the Southeastern Region — with 20, 12, and 5 million inhabitants respectively.[12] The majority of state capitals are the largest cities in their states, except for Vitória, the capital of Espírito Santo, and Florianópolis, the capital of Santa Catarina. There are also non-capital metropolitan areas in the states of São Paulo (Campinas, Santos and the Paraíba Valley), Minas Gerais (Steel Valley), Rio Grande do Sul (Sinos Valley) and Santa Catarina (Itajaí Valley).[13]

According to Statistics Canada, an urban area in Canada is an area with a population of at least 1,000 people where the density is no fewer than 400 persons per square kilometre (1,000/sq mi).[16] If two or more urban areas are within 2 km (1.2 mi) of each other by road, they are merged into a single urban area, provided they do not cross census metropolitan area or census agglomeration boundaries.[17]

In the Canada 2011 Census, Statistics Canada redesignated urban areas with the new term "population centre";[18] the new term was chosen in order to better reflect the fact that urban vs. rural is not a strict division, but rather a continuum within which several distinct settlement patterns may exist. For example, a community may fit a strictly statistical definition of an urban area, but may not be commonly thought of as "urban" because it has a smaller population, or functions socially and economically as a suburb of another urban area rather than as a self-contained urban entity, or is geographically remote from other urban communities. Accordingly, the new definition set out three distinct types of population centres: small (population 1,000 to 29,999), medium (population 30,000 to 99,999) and large (population 100,000 or greater).[18] Despite the change in terminology, however, the demographic definition of a population centre remains unchanged from that of an urban area: a population of at least 1,000 people where the density is no fewer than 400 persons per km2.

Since 2000, China's cities have expanded at an average rate of 10% annually. It is estimated that China's urban population will increase by 292 million people by 2050,[1] when its cities will house a combined population of over one billion.[21] The country's urbanization rate increased from 17.4% to 46.6% between 1978 and 2009, a scale unprecedented in human history.[22] Between 150 and 200 million migrant workers work part-time in the major cities, returning home to the countryside periodically with their earnings.[23][24]

Today, China has dozens of cities with one million or more long-term residents, including the three global cities of Beijing, Hong Kong, and Shanghai; by 2025, the country will be home to 221 cities with over a million inhabitants.[21] The figures in the table below are from the 2008 census, and are only estimates of the urban populations within administrative city limits; a different ranking exists when considering the total municipal populations (which includes suburban and rural populations). The large "floating populations" of migrant workers make conducting censuses in urban areas difficult;[25] the figures below include only long-term residents.

Similar to other Nordic countries, an urban area (taajama in Finnish) in Finland must have a building at least every 200 m (660 ft) and at least 200 people. To be considered a town or a city (kaupunki) for statistical purposes, an urban area must have at least 15,000 people. This is not to be confused with the city / town designation used by municipalities.[27][28]

In France, an urban area (Fr: aire urbaine) is a zone encompassing an area of built-up growth (called an "urban unit" (unité urbaine)[29] - close in definition to the North American urban area) and its commuter belt (couronne périurbaine). Americans would find the INSEE definition of the urban area[30] to be similar to their metropolitan area, and the INSEE sometimes uses the term aire métropolitaine[31] to refer to the country's largest aires urbaines.

Source: A PDF file named '1. Data Highlight' accessed on 11 April 2012 from Census of India, 2011[34] The figure below is the population statistic for the year 2011. This is a list of city population and it does not indicate urban agglomeration population.

Statistics New Zealand defines urban areas in New Zealand, which are independent of any administrative subdivisions and have no legal basis.[38] There are three classes of urban area: main urban areas are the 17 urban areas which have a population of 30,000 or more; secondary urban areas are the 14 urban areas which have a population of 10,000 or more but less than 30,000, and minor urban areas are the 103 urban areas which have a population of 1,000 or more but less than 10,000. Urban areas are reclassified after each Census, so population changes between censuses does not change an urban area's classification. For example, Rolleston (pop. 13,100) is still classified as a minor urban area because its population was under 10,000 at the 2013 Census.

Statistics Norway defines urban areas ("tettsteder") similarly to the other Nordic countries. Unlike in Denmark and Sweden, the distance between each building has to be of less than 50 m, although exceptions are made due to parks, industrial areas, rivers, and similar. Groups of houses less than 400 m from the main body of an urban area are included in the urban area.[40]

As per Republic Act No. 9009, in order to become a city, a local government unit must :

locally generated income of at least ₱ 100 million (based on constant prices in the year 2000) for the last two consecutive years, as certified by the Department of Finance, AND

a population of 150,000 or more, as certified by the National Statistics Office (NSO); OR a contiguous territory of 100 square kilometers, as certified by the Land Management Bureau, with contiguity not being a requisite for areas that are on two or more islands.

In Poland, official "urban" population figures simply refer to those localities which have the status of towns (miasta). The "rural" population is that of all areas outside the boundaries of these towns. This distinction may give a misleading impression in some cases, since some localities with only village status may have acquired larger and denser populations than many smaller towns.[42]

The largest cities of South Korea have an autonomous status equivalent to that of provinces. Seoul, the largest city and capital, is classified as a teukbyeolsi (Special City), while the next 6 largest cities (see the list below) are classified as gwangyeoksi (Metropolitan Cities; see Special cities of South Korea). Smaller cities are classified as si ("cities") and are under provincial jurisdiction, at the same level as counties (see:Administrative divisions of South Korea).

Urban areas in Sweden (tätorter) are statistically defined localities, totally independent of the administrative subdivision of the country. There are 1,956 such localities in Sweden, with a population ranging from 200 to 1,372,000 inhabitants.[55]

The figures below are the 2011 estimates for the twenty largest urban populations within administrative city limits; a different ranking exists when considering the total metropolitan area populations (in such rankings the Taipei-Keelung metro area is by far the largest agglomeration).

The United Kingdom's Office for National Statistics has produced census results from urban areas since 1951, since 1981 based upon the extent of irreversible urban development indicated on Ordnance Survey maps. The definition is an extent of at least 20 ha and at least 1,500 census residents. Separate areas are linked if less than 200 m (220 yd) apart. Included are transportation features.[56] The UK has five Urban Areas with a population over a million and a further sixty nine with a population over one hundred thousand.

In the United States, there are two categories of urban area. The term urbanized area denotes an urban area of 50,000 or more people. Urban areas under 50,000 people are called urban clusters. Urbanized areas were first delineated in the United States in the 1950 census, while urban clusters were added in the 2000 census. There are 1,371 urban areas and urban clusters with more than 10,000 people.

The U.S. Census Bureau defines an urban area as: "Core census block groups or blocks that have a population density of at least 1,000 people per square mile (386 per square kilometer) and surrounding census blocks that have an overall density of at least 500 people per square mile (193 per square kilometer)." [57]

The concept of Urbanized Areas as defined by the U.S. Census Bureau is often used as a more accurate gauge of the size of a city, since in different cities and states the lines between city borders and the urbanized area of that city are often not the same. For example, the city of Greenville, South Carolina has a city population just over 64,000 and an urbanized area population of over 400,000, while Greensboro, North Carolina has a city population just over 285,000 and an urbanized area population of around 310,000 — meaning that Greenville is actually "larger" for some intents and purposes, but not for others, such as taxation, local elections, etc.

In the U.S. Department of Agriculture's natural resources inventory, urban areas are officially known as developed areas or urban and built-up areas. Such areas include cities, ethnic villages, other built-up areas of more than 10 ac (4 ha), industrial sites, railroad yards, cemeteries, airports, golf courses, shooting ranges, institutional and public administration sites, and similar areas. The 1997 national resources inventory placed over 98,000,000 ac (40,000,000 ha) in this category, an increase of 25,000,000 ac (10,000,000 ha) since 1982.[60]